Apparatus for vacuum firing of porcelain dental articles



April 28, 1953 N. GQLD 2,636,915

APPARATUS FOR VACUUM FIRING OF PORCELAIN DENTAL ARTICLES Filed April 7, 1952 INVENTOR. M 6 o 2 TTORNEY Patented A r. 28, 1953 APPARATUS FOR VACUUM FIRING OF PORCELAIN DENTAL ARTICLES Nat Gold, Newark, N. J assignor to Nu-Dent Porcelain Studios, Inc., New York, N. Y., a corporation of New York Application April '7, 1952, Serial No. 280,990

8 Claims. 1

This invention relates to the art of firing dental articles such as porcelain jackets, crowns, and bridges by a novel method and apparatus providing a custom or personal service so that the dentist may send the articles to a laboratory equipped with the invention where following the teachings of this invention, the articles will be vacuum fired. The invention is not intended to provide production-line methods, such as are used in the fabrication of artificial teeth of standard sizes or types but is designed to provide a custom service for the dental profession.

Porcelain restorations fired pursuant to the invention have increased physical properties such as better impact and compressive strength, increased hardness, and greater density. It is found that restorations fired pursuant to the invention are free of entrapped air, which under conventional firing, forms air pockets and bubbles in the porcelain. Such pockets weaken the porcelain, make it porous, and disturb the natural surface reflection and refraction of the vitrified porcelain.

Porcelain fired pursuant to the present invention is found to have a vital brilliance and translucency in a range of hues embracing the spectrum of colors of natural teeth. In addition there is freedom from pits, pores, specks and bubbles, as indicated by photomicrographs taken of the porcelain vacuum fired articles, pursuant to the invention. The porcelain fired pursuant to the invention is in fact so hard and dense that if ground it may be refinished to a high glaze with a felt wheel. Pursuant to the invention, not only are the colors of teeth faithfully reproduced, but there are also provided the overtones which impart a living brilliance and translucency.

These and other advantageous objects, which will appear from the drawings and from the description hereinafter, are accomplished pursuant to the invention, of which an embodiment is illustrated in the drawings. It will be apparent, from a consideration of said drawings and the following description, that the invention may be embodied in other forms suggested thereby, and such other forms as come within the scope of the appended claims are to be deemed within the scope and purview of the instant invention.

In the drawings:

Fig. l is a perspective view of a device embodying the invention, taken on line ll of Fig. 4,

Fig. 2 is a fragmentary, perspective view thereof, taken on line 22 of Fig. 5,

Fig. 3 is a schematic view of one form of valve 2 mechanism which may be used to control the pump which may be employed in carrying out the invention,

Fig. 4 is a top plan view, taken on line ll of Fig. 1,

Fig. 5 is a front elevational view, partly fragmentary, of a portion of the device embodying the invention,

Fig. 6 is a partly fragmentary perspective view of furnace heating elements which may be used in carrying out the invention, and

Fig. '7 is a similar view of a furnace with heating elements shown partly exposed, embodying the invention.

As shown in the drawings, the device of the invention comprises a complete unit l0 adapted to be set up in a laboratory for the firing of porcelain crowns, jackets and porcelain bridges under high vacuum, pursuant to the invention described below, a high temperature of the order of around 2500" F.

The device is provided with suitable controls, as illustrated in the drawings, which may be varied from the specific forms shown, as will be apparent to those skilled in the art, the disclosure being of a preferred form of the invention.

The unit It! preferably comprises a rectangular housing ll having an opening I2 at one end thereof, mounted, for example, by means of suitable supports H3 or the like, on a work bench M or the like, which may be set up in a laboratory, the invention, as above noted, being intended for custom work. Pursuant to the present invention, the apparatus described herein may be set up in laboratories which would receive the porcelain crowns, jackets and bridges from dental practitioners by mail or other delivery; a ceramist in the laboratory would personally fire the jackets and bridges individually. The dentist may provide the ceramist with specific instructions with regard to shade selection, staining, etc. and may collaborate with the ceramist at the work bench. A door 15 is provided for closing the opening l2 in the housing ll, said door being preferably hingedly connected as at It to suitable bearings I! on the front wall 18 of the housing H. The door is preferably provided with a latch bar I!) pivotally connected thereto as at 20, the latch bar being offset as at 2| so that the free end 22 thereof may be received in the slot 24 of the closure plate 23. The door I5 is adapted to be thus closed to form a complete seal against the face or front wall l8 of the housing II. If desired, a suitable gasket may be secured to the door or front wall of the housing to further cooperate in closing the opening 12, that being a matter within the choice of the user. A correspondingly rectangular heating chamber 3! of lesser dimensions than the interior walls of housing ii is secured interiorly of the housing in concentrically spaced relation thereto by suitable brackets (not shown). It is found, in practice, that the rectangular crosssection of the housing I! and of the heating chamber 3!, and the concentric, disposition of. the latter within the former provides a deadair space 32 surrounding the heating chamber 38 in the housing ll, reducing to an absolute minimum loss of heat, which is an essential factor in the high temperature device of this invention. The chamber 3! is provided with anopening 33 (Fig. l) which is disposed in alignment with the opening iii of the housing ii in the completed device as shown in Fig. l. A platform Ed is positioned in the housing It in alignment with the opening l2 thereof and intermediate the same and the opening 3.3 of the heating chambertl, so that the cerarnist may use platform 3.4 to receive porcelain crowns, jackets, bridges, etc. upon said platform temporarily, preferably by use of suitable grasping tools, for insertion into and removal from chamber 3!, from time to ti: e. The platform it is secured to the housing H by suitable means as, for example, by one or more vertical supports 35, secured to the platform and unitary with one or more support bars 35 fixed to the interior bottom wall of the housing H, or the said members 35, 38 maybe provided with complementary slots through which bolt or f-) other means 3'5 may be passed, whereby platform 3 may be adjustably positioned at such predetermined point in the housing relative to the openings l2, as is found convenient. Heating chamber 3i means, as for example, a door 3.8, which may be positioned on the platform Sl to be moved by the operator against the opening 33 to close the latter, and to thus seal the firing interior closure at of the chamber 3i. be embedded in the walls oi chamber 3! or on separate heating plates 33 as in Fig. 6; said elements may be platinum or other suitable material, and may beconnected to .a suitable source of current by an electric cord (not shown). An r on-ofi switch ill may be cut into said cord at any suitable point so as to provide control for the operator. A further control may be provided by means of a thermocouple switch or similar means operable to open the circuit when the temperature in the chamber ti attains a predetermined desired thermal degree. A suitable transformer i2 may be provided with a rheostat control @3 cperable by the operator with suitable pyrometer, vacuum, etc. gauges ill, 3 5 connected to the deice to indicate such conditions as temperature and vacuum attained.

Pursuant to the invention a vacuum pump at is provided, connected to the interior 32 of the housing i! as by means of the pipe By this arrangement a high vacuum may be provided in the housing it. It is found in practice that this high vacuum evacuates all air from the porcelain and also provides an absolutely dustiree atmosphere. A suitable switch 58 is provided for the pump it, said switch being provided with an actuating switch arm 5i, normally urged outwardly to the position shown in Fig. 2, in which position switch 5t will beopen so that the pump "it will not be actuated. The arm 5! may be provided with closure 1 Heating elements it may 4 is preferably provided with a roller 52 at the end thereof. To actuate the pump it, and close the switch 50, the arm 5! of said switch is moved into the switch. Pursuant to the invention, the means for actuating the switch is combined with a valve 53 which is shown schematically in Fig. 3, connecting pipes ti andpipe 31 the latter being connected to the interior 32 of the housing H as at 5d indicated in Fig. 5. An exhaust valve 53 may be connected as at 5'5 to pipe ti below valve, 53. Thus the operator on opening exhaust valve 56 by rotating the thumbpiece 58, may permit the entry of atmospheric air into the housing l! to relieve the vacuum when desired, as, for example, after the baking or firing operation has been completed and before opening the door 35. It will be apparent from the foregoing description that a three-way valve 62, as shown in Fig. 3, connecting the members tL- ll and pipe leading to the atmosphere may be substituted for the valvesst, 55 above described.

A lever til is keyed to valve 53, the parts being so juxtaposed that on rotation of the lever fill its rotational arc will bring it into registry with the free end 52 of the switch arm 5!. Thus by raising the lever to, the operator may at once connect the sections ti, il of pipe so that the interior 32 of the housing 5 i will be connected to the pump at and the switch til will be actuated to cause a pumping action to occur, to create the desired vacuum in the housing ll. After suilicient vacuum has been attained as noted on suitable gauges etc, the lever 6!! would be moved away from the switch 5 l, whereupon the pumping action would be stopped and the interior of the housing ll sealed by valve 53. It will be apparent from the foregoing that the operator may, pursuant to the invention, provide precisely the desired temperature and vacuum conditions and may readily break or restore the vacuum, all within short periods of time. Any other form of switch may be used in place or" switch 56 above described, suitable for the attainment of the same end, within the spirit and scope of this invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. A laboratory device for custom firing of porcelain jackets and bridges, comprising a rectangular housing having an cpcnin at one end, means defining a rectangular furnace heatin chamber interiorly disposed in the housing in spaced relation to the i ner walls of the housing so as to define a cont 5 air space between the furnace heating char... er and the inner walls of the housing completely surrounding the furnace heating chamber, chamber being closed except for an opening at one end, a flat platform to hold the articles to be fired, means to mount the platform intericrly oi the housing means to vertically adjust the relation of the platform to the openings thereof and of the heating chamber, and in alignment therewith, a door positioned on said platform to be moved against the opening to substantially close the same, electrical elements in said ChEtlZlher to heat the latter, means connect said ele ments to a source c .'.-ent, means to regulate such current, aclosure door sealing the opening of said housing, an air pump, a pipe connecting the pump to the interior of the device for the evacuation of air tier-of: en, a switch to control the actuation of the pump, an arm on said switch normally projecting therefrom to open the switch, a lever so juxtaposed relative to the switch not; c.

arm as to engage the latter when the lever is rotated to move the arm into the switch to actuate the switch, a valve keyed to the lever and cut into said pipe whereby, when said lever is in one position, the pump pipe will be actuated and connected to the interior of the device, and at another position, the pump will be shut off and sealed from the device.

2. A laboratory device for custom firing of porcelain jackets and bridges, comprising a housing having an opening at one end, means defining a furnace heating chamber interiorly disposed in the housing in spaced relation to the inner walls of the housing so as to define an air space between the furnace heating chamber and inner walls of the housing completely surrounding the furnace heating chamber, said chamber being closed except for an opening at one end, a fiat platform to hold the articles to be fired, electrical elements in said chamber to heat the latter, means to connect said elements to a source of current, means to regulate such current, a closure door for sealing the opening of said housing, an air pump, a pipe connecting the pump to the interior of the device for the evacuation of air therefrom, a switch to control the actuation of the pump, a lever so juxtaposed relative to the switch as to engage the latter when the lever is rotated to actuate the switch, a valve keyed to the lever and cut into the said pipe whereby, when said lever is in one position, the pump pipe will be actuated and connected to the interior of the device, and at another position, the pump will be shut off and sealed from the device.

3. A laboratory device as set forth in claim 2, a second valve leading to the atmosphere and connected to the pipe which connects the pump with the interior of the device at a point below the first mentioned valve, whereby, when said second valve is opened, atmospheric air will be admitted into the device to break the vacuum thereof.

4. A laboratory device as set forth in claim 2, said heating chamber being concentrically disposed in said housing.

5. A dental laboratory device for custom firing of porcelain jackets and bridges, comprising a rectangular housing having a constricted opening at one end, means defining a rectangular furnace heating chamber interiorly disposed in the housing in spaced relation to the inner walls of the housing, said chamber being closed except for a constricted opening at one end so as to define an air space between the furnace heating chamber and inner walls of the housing completely surrounding the furnace heating chamber, a fiat platform to hold the articles to be fired, disposed in the furnace intermediate the openings of the housing and chamber and in alignment therewith, electrical elements in said chamber to heat the latter, means to connect said elements to a source of current, means to regulate such current, a, closure door for sealing the opening of said housing, an air pump, a pipe connecting the pump to the interior of the device for the control of the air therein, and means to selectively actuate the pump and connect it to the interior of the device, or to selectively shut off the pump and seal it from the interior of the device, or to selectively connect the interior of the device to the atmosphere.

6. A dental laboratory device for custom firing of porcelain jackets and bridges, comprising a rectangular housing having a constricted opening at one end, means defining a rectangular furnace heating chamber interiorly disposed in the housing in spaced relation to the inner walls of the housing so as to define an air space between the furnace heating chamber and inner walls of the housing completely surrounding the furnace heating chamber, said chamber being closed except for a constricted opening at one end, a flat platform to hold the articles to be fired, disposed in the furnace intermediate the openings of the housing and chamber and in alignment therewith, means to heat the chamber, an air pump, a pipe connecting the pump to the interior of the device for the control of the air therein, valve means cut into said pipe and switch means for said pump, said valve and switch means being operable to selectively actuate the pump and connect it to the interior of the device, or to selectively shut off the pump and seal it from the interior of the device.

7. A dental laboratory device for custom firing of porcelain articles, comprising a housing having an opening at one end, a furnace heating chamber of corresponding outline but of smaller size disposed in the housing in concentrically spaced relation to the inner walls thereof so as to define an air space between the furnace heating chamber and inner walls of the housing, completely surrounding the furnace heating chamher, said chamber being closed except for an opening at one end, means to heat said chamber, a platform to hold articles to be fired disposed in the housing intermediate the openings of the housing and. chamber, and in alignment therewith, a closure door unit adapted to be slid on the housing platform relative to the chamber opening for sealing the opening of said housing, an air pump, a pipe connected to the pump and means to selectively connect said pipe to the interior of the device and to actuate the pump, and to selectively disconnect said pipe and shut off the pump.

8. A dental laboratory device for custom firing of porcelain articles, comprising a housing having an opening at one end, a furnace heating chamber disposed in said housing in spaced relation to the inner walis thereof, said chamber having an opening at one end, means to heat said chamber, a platform, to hold articles to be fired, disposed in the housing intermediate the open ends of the housing and chamber, a closure door for sealing the opening of said housing, an air pump, and means to connect the pump to the interior of the device.

NAT GOLD,

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 817,212 Wingren Apr. 10, 1906 1,065,326 Marshall June 17, 1913 1,515,234 Woodson Nov. 11, 1924 1,617,359 Westberg Feb. 15, 1927 1,724,956 Monckton Aug. 20, 1929 1,994,917 McG-regor Mar. 19, 1935 2,039,165 Hayakawa Apr. 28, 1936 2,252,052 Van Embden Aug. 12, 1941 

